Field of the Invention
The present invention relates to a three-dimensional measuring apparatus.
Background Art
Generally, when electronic components are mounted onto a printed substrate, cream solder is first printed on a predetermined electrode pattern disposed on the printed substrate. Next, the electronic component is provisionally set on the printed substrate according to the viscosity of the cream solder. Thereafter, soldering is performed by putting the printed substrate into a reflow furnace and performing a predetermined reflow process. Recently, an inspection of the printed state of the cream solder is required as a prior step to introducing into the reflow furnace, and a three-dimensional measuring apparatus is used in the inspection.
In recent years, proposals have been made for a variety of three-dimensional measuring apparatuses including those known as a non-contact type which uses light, and technology that relates to, for example, a three-dimensional measuring apparatus that uses a phase shift method is proposed.
Three-dimensional measuring apparatuses that use a phase shift method irradiate a light pattern having a sinusoidal (banded) light intensity distribution by irradiating unit made by combining a light source with a filter having a sine wave pattern. Further, observing is done using an imaging unit disposed directly above a point on the substrate. A CCD camera or the like made up of a lens, an imaging element, and the like may be used as the imaging unit. In this case, the light intensity I is given according to the below equation for the measuring point P on the screen.I=B+A·cos φ
[Where B is direct current optical noise (offset component), A is a contrast of a sine wave (reflectance ratio), and φ is a phase given due to the unevenness of the object]
At this time, the light pattern is moved to change the phase in, for example, four steps (φ+0, φ+π/2, φ+π, and φ+3π/2), and images that have intensity distributions I1 , I2, I3, and I4 that correspond to these are incorporated to obtain the modulated portion (position information for driving height) θ based on the equation given below.θ=arctan {(I4−I2)/(I1−I3)}
Using this modulated portion θ, the three-dimensional coordinates (X, Y, Z) for the measuring point P can be found for the cream solder on the printed substrate, and the three-dimensional shape, particularly the height, of the measuring target can be measured.
In recent years, various technologies have been proposed (for example, see Patent Documents 1 and 2) where, in order to improve measurement accuracy, in addition to acquiring one set of image data (for example, four image data) for conventional three-dimensional measuring as described above, image data imaged under a different irradiating light than the light pattern used at the time of imaging the one set of image data is acquired separately.